Fluid pump or motor



D. L. YARGER 3,150,603

FLUID PUMP OR MOTOR Sept. 29, 1964 2 Sheets-Sheet l Filed Apr i1 so, 1962 a W P Sept. 29, 1964 3,150,603

D. L. YARGER FLUID PUMP 0R MOTOR Filed April 30, 1962 2 Sheets-Sheet 2 W a ///,f

United States Patent 3,150,603 FLUID PUMP OR MOTOR Donald L. Yarger, 342 Elm Ave., Marengo, Ill. Filed Apr. 30, 1962, Ser. No. 191,101 14 Claims. (Cl. 103-174) This invention relates to fluid pumps or motors and particularly to a multiple piston type pump or motor.

An important object of this invention is to provide a multiple piston type fluid pump or motor which is adapted for low speed operation with substantially no slip.

Another object of this invention is to provide a multiple piston type fluid pump or motor having valves on the pistons for valving the flows of fluid to and from the cylinders in sequential phased relation, and in which the valving is so arranged as to minimize leakage between the fluid inlet and return lines.

Another object of this invention is to provide a multiple piston type fluid pump or motor having piston controlled valve means for sequentially valving the flows of fluid to and from the several cylinders, and which valve means avoids reversal of the fluid through the valving passages to achieve more positive and efiicient operation.

A more particular object of this invention is to provide a multiple piston type fluid pump or motor having inlet Valve means on certain of the pistons for valving the flows of fluid to each of the several cylinders, and outlet valve means on others of the pistons for valving the flows of fluid from the several cylinders whereby the inlet and outlet valving functions are segregated to minimize leakage between the fluid inlet and outlet lines for the pump or motor.

A further object of this invention is to provide a radial piston type pump or motor having a cam for controlling reciprocation of the piston and which is so arranged as to substantially avoid scuffing of the piston on the cam.

A still further object of this invention is to provide a piston type pump or motor in which the pistons are turned on their axes during operation to achieve substantially uniform wear on the pistons.

Yet another object of this invention is to provide a multiple piston type fluid pump or motor having a crankshaft disposed in a closed crankcase chamber for sequentially reciprocating the several pistons, and which pump or motor is arranged for reversible operation and has an improved arrangement for venting the crankcase to the fluid inlet line, independent of the direction of the pump or motor.

These, together with various ancillary objects and advantages of this invention will be more readily appreciated as the same becomes better understood by reference to the following detailed description when taken in connection with the accompanying drawings wherein:

FIG. 1 is a transverse sectional view through the fluid pump or motor and with the valving passages shown diagrammatically to illustrate the construction and operation;

FIG. 2 is a fragmentary longitudinal sectional view through the fluid pump or motor, taken on the plane 22 of FIG. 1;

FIG. 3 is a transverse sectional view through the pump or motor, taken on the plane 33 of FIG. 2 and illustrating certain of the valve passages;

FIG. 4 is a fragmentary sectional view taken on the plane 4-4 of FIG. 2, and illustrating another of the valve passages; and

FIG. 5 is a fragmentary sectional view through a modified form of pump or motor.

The apparatus of the present invention is adapted for use as either a fluid pump or motor. However, for convenience in describing the invention, it is hereinafter generally referred to as a fluid motor and may be used with either liquid or gaseous fluids such as oil and air. The motor in general includes a plurality of cylinders which, for reasons set forth hereinafter, are arranged in groups of four or multiples thereof. In the form shown, four cylinders are provided and are designated 11, 12, 13 and 14. Piston members 15-18 are slidably disposed in the cylinders and have valve means thereon for controlling the flows of fluid to the several cylinders. The pistons and the valve means thereon are sequentially reciprocated in a preselected phase relation to each other by a means such as a cam mounted on a shaft 21. In accordance with the present invention, the valve means on two of the pistons are arranged to valve the flows of fluid to each of the four cylinders and the valve means on the other two pistons are arranged to valve the flows of fluid from each of the four cylinders so that the valving functions for the supply and discharge of fluid to each cylinder are separated. This arrangement simplifies the valving passages, minimizes leakage between the fluid supply and return lines, and avoids flow reversal of the fluid in the valving passages to achieve more positive and efiicient operation. While the cylinders and pistons can be arranged in various different relations with respect to a cam means 20 to achieve sequential reciprocation of the pistons in substantially phase relation to each other, and may, for example, be arranged with the cylinders in-line and the piston driven by a series of aligned cams on a cam shaft; or arranged with the cylinders generally parallel and the pistons driven by a wobble-plate type cam, the cylinders and pistons are advantageously arranged as shown in the drawings to extend generally radially of the annular cam.

Referring more specifically to the drawings, the motor includes a casing 25, conveniently in the form of a casting having a generally annular hub portion 26 and four outwardly projecting bosses 27. The cylinders 11- 14 are in the form of bores which extend through the bosses and intersect a crank chamber 28 in the hub portion 26. The outer ends of the bores may be closed in any'desired manner and, as shown, have caps 29 threadedly mounted therein and sealed as by an O-ring 31. The piston members 15-18 are slidably disposed in the cylinder bores and define chambers 32-35 in the outer ends of the cylinders 11-14 respectively. The shaft 21 is rotatably mounted in bearings 38 and 39 in the hub portion 26 and the cam means 20 is attached to the shaft for rotation therewith. A conventional shaft seal 40 is provided on the hub 26 to form a running seal with the shaft. In the form shown, the cam means includes an inner eccentric portion 41 which is non-rotatably keyed by a key 42 to the shaft, and an outer bearing portion 43 which is rotatable relative to the inner portion 41. Alternatively, the cam means can be formed integral with the shaft, or otherwise secured thereto. The inner ends of the piston members 15-18 engage the periphery of the cam member 20 so that the cam member controls reciprocation of the piston members. In the form shown wherein the cylinders extend generally radially of the shaft, the cylinders are angularly spaced apart substantially 90 from the adjacent cylinders so that the piston members are sequentially reciprocated in substantially 90 phase relation to each other. During operation, the fluid pressure in the piston chambers 32- 35 will urge the piston members inwardly into engagement with the cam. However, in order to initially position the piston members prior to starting the motor, light springs 45 are provided in the piston chambers and are conveniently seated in recesses 46 and 47 in the caps and piston members respectively to yieldably urge the piston members into engagement with the cam.

In order to operate the device as a fluid pump or motor, it is necessary to sequentially valve the flows of fluid to and from the piston chambers in timed relation with the reciprocation of the piston members. The valve means is advantageously provided on the piston members intermediate the ends thereof and, in accordance with the present invention, the valve means on two of the pistons is arranged to control the flows of fluid in one direction to each of the four piston chambers and the valve means on the other two pistons is arranged to control the flow of fluid in the other direction from each of the four piston chambers. More particularly, each of the cylinders 11-14 are provided with a main inlet port designated 51-54 respectively, and which main ports communicate with the respective cylinders intermediate the ends thereof. The cylinders 11-14 are also provided with first and second control ports designated 51a and 51b; 52a and 52b; 53a and 53b; and 54a and 54b, respectively. Each of the piston members 1518 is provided with valve passages, herein shown in the form of a peripheral groove 56 in each of the piston members and which define spaced valve faces 57 and 58. As is apparent from FIG. 1, the valve passage in each piston member is arranged to communicate the main port alternately with the respective first and second control ports as the piston members reciprocate. With this arrangement, one pair of piston members such as 15 and 17 are reciprocated 180 out of phase with each other and the other'pair of piston members 16 and 18 are similarly reciprocated 180 out of phase with each other, and 90 out of phase with the piston members 15 and 17. A first main flow passage 61 is provided in the easing for communicating the main ports 51 and 52 with each other and with a fitting 62. A second main passage 63 is also conveniently provided in the casing and communicates the main ports 53 and 54 with each other and with the second fitting 64. Either one of the main passages 61 or 63 can function as an inlet passage and the other function as an outlet passage to enable reversible operation of the apparatus as either a pump or motor. As shown, the fitting 62 is connected through a conduit 65 with a flow reversing valve 66 and the fitting 64 is similarly connected to a conduit 67 with the flow reversing valve. The flow reversing valve 'has inlet and dischargelines 67 and 68, and the valve 66 is selectively operable to communicate either of the lines 65 and 67 with the inlet and return lines 67 and 68. For operation as a pump, one ofthe conduits such as 67 can be connected to .a supply source and the other conduit 68 function as a pressure delivery line. For operation as a motor, fluid under pressure can be supplied to one of .the conduits such as 67 while the other conduit 68 functions as a return'line. It will thus be seen that when the device is operated as either a pump or motor, fluid will flow into one of the valve'means on two of the pistonmembers which are reciprocated 90 out of phase with each other and fluid will'flowfrom the valve means on'the other two piston members which are operated 90 out of phase with each other.

Control passages are provided for connecting the several valve means to the piston chambers, and the control passages are so arranged that the valve means on one .piston member will control the flow of fluid in one direction alternately to the piston chambers for the two piston members which are operated 90 out of phase therewith. More particularly, a first pair of control passages designated 71 and 72 are arranged to connect the piston chamber 32 with the control ports 52a and 54a associated with piston members 16 and 18 respectively. A second pair of control passages designated 73 and 74 communicate piston chamber 34 with the control ports 52b and 54b associated with the piston members 16 and 18. Similarly, a third pair of control passages 75 and 76 connect the piston chamber 33 with the control ports 51b and 53b, and a fourth pair of control passages designated 77 and 78 connect the piston chamber with the control ports 51a and 53a. Thus, assuming 4 that the flow reversing valve 66 is operated so that conduit is the inlet conduit and conduit 67 is the discharge conduit, it will be seen that the valve on piston member 15 valves the flow of fluid to each of the piston chambers 33 and 35 disposed at right angles thereto, and the valve on piston member 16 valves the flow of fluid to each of the piston chambers 32 and 34. Discharge of fluid from the four piston chambers is under the control of the valves on piston members 17 and 18, the valve on piston member 17 valving the flow of fluid from piston chambers 33 and 35 and the valve on piston member 18 valving the flow of fluid from piston chambers 32 and 34. Since the valving of the flow of fluid to the piston chambers and the valving of the fiow of fluid from the piston chambers is performed by dilferent piston members at all times, the leakage of fluid from the inlet to the return line is minimized. In addition, for any given direction and mode of operation, fluid will always flow in the same direction through the control passages 71-78 so as to avoid fiow reversal in these passages each time the piston member reciprocates. Since the valve means on each piston member alternately supplies or exhausts fluid from the two diametrically opposed piston chambers, it is essential to proper operation that the valve means shut off the flow to or from one cylinder before communicating the main port with the other cylinder to prevent by-passing of fluid from the inlet control port to the outlet control port. For this purpose, it is preferable to arrange the spacing between the valve faces 57 and 58 on each piston member so as to be slightly less than the spacing between the respective control ports. With this arrangement, the valve faces on the piston members will momentarily block flow from the main port to both of the respective control ports at the mid stroke of each piston, that is when the pistons are disposed substantially 90 from the top or bottom dead center as shown in connection with pistons 16 and 18 in FIG. 1. This slight overlap, however, is not harmful to operation since, at the time each valve means overlaps the respective control ports, the piston vmember which carries that valve means is moving at a relatively high speed, while the pistons in the chambers controlled by that valve means are at either top or bottom dead center and are moving at a relatively low speed. The rate of change of volume in the corresponding piston chambers is therefore small during the time that the valve members overlap both of the control ports.

As previously mentioned, the casing is conveniently formed from a casting. In order to provide proper operation, it is necessary that the first and second control ports associated with each cylinder be spaced a corresponding distance from the axis of the shaft 21. These control ports are conveniently formed during casting so as to minimize the machining operations required. It has been found that proper spacing of the control ports with respect to the axis of the shaft can be maintained if the single core which forms the crank chamber 28, the cylinder bores and the control ports is accurately formed. A simple control passage arrangement which facilitates casting of the control passages in the casing 25 is illustrated in FIGS. 3 and 4. As shown therein, the pairs of control passages 71 and 72, and the pair of control passages 73 and 74 are formed in the casing at one side of the cylinders and the pair of control passages and 76 and the pair of control passages 77 and 78 are formed in the casing at the other side of the cylinders. The pairs of control passages each have a generally Y-shaped configuration and intercommunicate the respective control ports and piston chambers without crossing or overlapping each other.

While a four cylinder apparatus has been disclosed, it is apparent that the apparatus could be modified to provide eight or other multiples of four cylinders, so

long as the valve means on each piston controls the flow to the two piston chambers which are substantially out of phase therewith. In FIG. 2, two motors are shown mounted in tandem. The second motor is generally the same as the first mentioned fluid pump or motor, and like numerals followed by the suflix are used to designate corresponding parts. Thus, the second motor includes a casing having at least four cylinders such as 13' therein and a piston member such as indicated at 17' in the cylinders. The pistons are reciprocated in timed relation to each other by a cam means 20' conveniently attached to the shaft 21. In accordance with the present invention, the second motor unit is advantageously arranged to be operated under the control of the valves on the first mentioned unit. For this purpose, the valves have been omitted from the second unit and each of the piston chambers such as 34' are merely connected through a passage 70 with the corresponding piston chamber such as 34 in the first mentioned unit. Thus, the valve means on the pistons 15-18 will also operate to sequentially valve the flows of fluid to the pistons of the second unit to operate the same in synchronism with the first unit. Obviously, additional pump or motor units can be arranged in a like manner on either side of the main unit, to be operated under the control of the valves of the main unit.

Some fluid will leak past the pistons into the crank chamber, due to the working clearance between the parts and an improved arrangement is provided for draining the crankchamber without requiring a separate external drain, and in such a manner as to drain the excess fluid in the crank chamber independent of its mode or direction of operation. As shown in FIG. 1, drainpassages 82 and 83 are provided in the casing to communicate the crankchamber 28 with the main passages 61 and 63 and have valve seats therein. Check valves 84 and 85 are yieldably urged by springs 86 and 87 against the seats to block flow to the crankchamber and to open for flow from the crankchamber. As shown, the springs are held in position by suitable retainers which are open to permit flow therepast. With this arrangement, either check valve 84 or 85 will open to pass fluid from the crankcase chamber 28, dependent on which of the lines 65 or 67 is the low pressure line. The pressure in the other of the lines will, of course, hold the other check valve closed to block flow from the high pressure line into the crank case chamber.

A modified form of the pump or motor is illustrated in FIG. 5. The pump or motor is generally the same as that shown in FIGS. 1-4 and like numerals are used to designate corresponding parts while modified parts are designated by the suflix In the generally radial type piston pump or motor illustrated, problems are encountered in scufling of the pistons on the cam or cam bearing member 43. From FIG. 1, it will be seen that the point of contact, between the cam or cam bearing 43 and the end of the several pistons, shifts in a direction crosswise of the pistons as the cam rotates. This produces a scuffing action which causes wear and also applies lateral pressures to the pistons. In order to overcome this scufling action, the end of the pistons and the face of the cam bearing are arranged so that the line of contact between the piston and cam bearing is inclined slightly to a plane perpendicular to the piston axis and extends generally radially of the piston so that the piston tends to turn or roll on its axis as the cam rotates. This achieves a generally rolling contact between the piston and cam and reduces the wear between the piston and cam while also turning the piston in its bore to achieve uniform wear on the piston and cylinder.

As shown in FIG. 5, the cylinder bore such as 13" is inclined at a shallow angle to a plane perpendicular to the shaft 21 and the end 90 of each piston such as 17" is made slightly conical to engage the cam bearing 43 along a line extending generally radially of the piston and inclined to the longitudinal axis of the piston. This produces the aforedescribed turning of the piston about its axis in the bore to minimize scuffing and wear between the piston and cam bearing. While the cam 41 could be of the one piece type, it is preferable to employ the outer cam bearing 43 which is rotatable relative to the cam as the latter turns. When the cam 41 is rotated at a relatively high speed, the outer cam bearing will only rotate at a very low speed and the cam can even be formed with flats on its outer surface which engages the piston to inhibit all rotation of the cam bearing. This minimizes the speed at which the piston is turned about its axis. The angle of the piston relative to the cam also effects the speed at which the piston turns on its axis, and this angle is made relatively small. In the device illustrated, an angle of about 4 degrees has been found satisfactory. If the cam bearing is formed with the aforedes'cribed flats, or is otherwise constrained against turning, the pistons will merely oscillate about their axes as the cam rotates. In order to avoid twisting of the springs such as 45, a preferably semi-spherical seat member 91 is provided between the spring and the piston.

In certain applications wherelong life is desired, it is advantageous to provide a sleeve liner in the cylinder bores. As shown in FIG. 5, a liner 92 is provided in the cylinder bores and has openings 93, 94 and 95 therein arranged to respectively communicate with the first control port such as 5312, the main port such as 53 and the second control port such as 53a of the cylinder. As shown, the sleeve is axially positioned by a shoulder 96 formed on the casing, and which shoulder is preferably machined in preselected relation to the walls of the crankchamber 28 so that the sleeve will be positioned in proper relation to the crankshaft 21. With this arrangement it will be noted that the sleeve can accommodate minor inaccuracies in the coring and casting of the casing and the control ports. In order to minimize leakage around the pistons, sealing rings such as the O-rings 97 and 98 may be provided, if desired.

From the foregoing, it is thought that the operation and construction of the device will be readily understood. As previously described, two of the pistons which are reciprocated out of phase with each other control the flows of fluid in one direction to each of the four piston chambers and the other two piston members which are operated 90 out of phase with each other control the flow of fluid from each of the four piston chambers. The inlet and discharge valving functions are therefore effectively isolated from each other to minimize leakage between the supply and return lines and to also achieve unidirectional flow through each of the control passages, during operation of the unit as a pump or motor.

I claim:

1. A rotary piston type fluid pump or motor comprising a pump casing defining at least four cylinders, first, second, third and fourth piston members slidably disposed in said cylinders and defining a piston chamber at one end of each cylinder, fluid control means individual to at least each of said four piston members, said fluid control means each including a main control port and first and second ports and valve means operated by the respective piston member for communicating each main port alternately with the respective first and second control ports, a shaft, means on said shaft controlling reciprocation of said first, second, third and fourth piston members in successive substantially 90 phase relation, a first main passage communicating with the main ports of the fluid control means associated with said first and second piston members, a second main passage communicating with the main ports of the fluid control means associated with said third and fourth piston members, one of said main passages being an inlet passage and the other of said main passages being an outlet passage, and first and second control passages respectively individual to each said first and second control ports, the first and second control passages associated with each piston member being connected to the piston chamber for the two piston members operated at 90 phase relation to the piston member with which the first and second control passages are associated.

2. A rotary-piston type fluid pump or motor comprising, a pump casing defining at least four cylinders, first, second, third and fourth piston members slidably disposed in said cylinders and defining a piston chamber at one end thereof, fluid control means individual to at least each of said four piston members and including a main port and first and second control ports communicating with each of said four cylinders intermediate the ends of the piston member therein and valve means on each of the piston members for communicating the main port alternately with the first and second control ports, a shaft, means on said shaft controlling reciprocation of said piston members, to cyclically reciprocate the first, second, third and fourth piston members in successive substantially 90 phase relation, a first main passage communicating with the main ports associated with said first and second piston members, a second main passage communicating with the main-ports associated with the third and fourth piston members, one of said main passages being an inlet passage and the other of said main-passages being an outlet passage, and first and second control passages respectively individual to each said first and second control ports, said first and second control passage associated with each piston member being connected to the piston chambers for the two piston members operated at 90 phase relation to the piston member with which the first and second control passages are associated.

3. A rotary piston type fluid pump or motor comprising, a pump casing defining at least four cylinders, first,

second, third and fourth piston members slidably disposed in said cylinders and defining a piston chamber at one end thereof, fluid control means individual to at least each one of said four piston members and including a main port and first and second control ports communicating with each of said four cylinders intermediate the ends ofthepiston member therein and valve -means on each of the piston members for communicating the main port alternately with the first and second control ports, a shaft, means on said shaft controlling reciprocation of said piston members, to cyclically reciprocate the first, second and third and fourth piston members in successive substantially'90" phase relation, a first main passage communicating with the main ports associated with said first and second piston members, a second main passage communicating with the main ports associated .with the third and fourth piston members, one of said main passages being an inlet passage and the other of said main passages being an outlet passage, a pair of control passages connected to the first and second control ports associated with each piston member, the control passages associated with the first piston member being connected to the piston chambers for the second and fourth piston members; the control passages associated with the second piston member being connected to the piston chamber for the first and third piston members; the control passages associated with the third piston member being connected to the piston chambers for the second and fourth piston members; and the control passages associated with the fourth piston member'being connected to the piston chambers for the first and third piston members.

4. A rotary piston type fluid pump or motor comprising, a pump casing having at least four cylinders, first, second, third and fourth piston members slidably disposed in said cylinders and defining a piston chamber at one end thereof, fluid control means individual to at least each one of said four piston members, said fluid control means including a main port communicating with each cylinder intermediate the ends thereof and first and second control ports communicating with each cylinder at points spaced axially from relatively opposite sides of the respective main port, said piston members each ,valve faces for blocking flow for the main port alternately to said first control port and to said second control port, a shaft, means on said shaft controlling reciprocation of said piston members to cyclically reciprocate the first, second, third and fourth piston members in successive substantially phase relation, a first main passage communicating with the main ports associated with said first and second piston members, a second main passage communicating with the main ports associated with said third and fourth piston members, one of said main passages being a supply passage and the other of said main passages being a discharge passage, a first set of control passage means communicating the first and second control ports associated with the first and second piston members to the piston chambers for each said first, second, third and fourth piston members whereby the first and second piston members control the flow of fluid in one direction to the four cylinders, and a second set of control passages communicating the first and second control ports associated with the third and fourth piston members to the piston chambers for each said first, second, third and fourth piston members whereby the third and fourth piston members control the flow of fluid in the other direction to the four cylinders.

5. A rotary piston type fluid pump or motor comprising, a pump casing having at least four cylinders, four piston members slidably disposed in said four cylinders and defining a piston chamber at one end thereof, fluid control means individual to at least each one of said four piston members, said fluid control means including a main port communicaing with each cylinder intermediate the ends thereof; a first control port communicating with each cylinder at a point spaced axially from one side of the respective main port; a second control port communicating with each cylinder at a point spaced axially from the other side of the respective main port, a shaft; and passage means in each piston member for communieating the main port alternately with the respective first and second ports as the piston member reciprocates, means on said shaft for controlling reciprocation of said piston members to cyclically reciprocate a first pair of piston members substantially out of phase with each other and to cyclically reciprocate a second pair of piston members substantially 180 out of phase with each other and 90 out of phase with the piston members of said first pair, a first pair of control passages communicating said first ports associated with said first pair of piston members to the piston chamber for one of the piston members of said second pair, a second pair of control passages communicating said second control ports associated with said first pair of piston members to the piston chamber for the other .piston member of said second pair, a third pair of control passages communicating said first control ports associated with said second pair of piston members with the piston chamber of one for said piston members of said first pair, a fourth pair of control passages communicating said second control ports associated with said second pair of piston members with the piston chamber for the other piston member of said first pair, a first main passage communicating with one of the main ports associated with each said first and second pairs of piston members, and a second main passage communicating with the other of the main ports associated with each said first and second pairs of piston members, one of said main passages being a supply passage and the other main passage being a discharge passage.

6. A rotary piston type fluid pump or motor comprising a pump casing having a shaft and at least four cylinders-extending generally radially from the shaft and angularly spaced apart substantially 90 to provide first pair of cylinders disposed substantially 180 from each other and a second pair of cylinders disposed substanially 180 from each other and substantially 90 from the cylinders of the first pair, a piston member slidably disposed in each cylinder and defining a piston chamber therein, an eccentric cam means on said shaft for controlling cyclic reciprocation of said piston members in successive substantially 90 phase relation to each other, fluid control means individual to the piston members in at least each of said four cylinders, said fluid control means each including a main port communicating with each cylinder intermediate the ends thereof; a first control port communicating with each cylinder at a point spaced radially inwardly of the respective main port; a second control port communicating with each cylinder at a point spaced radially outwardly of the respective main port; and passage means in each valve member for communicating the main port alternately with said first and second control ports as the piston member reciprocates, a first pair of control passages communicating said first ports in said first pair of cylinders with the piston chamber in one cylinder of said second pair of cylinders, a second pair of control passages communicating the second control ports in said first pair of cylinders with the other cylinder of said second pair of cylinders, a third pair of control passages communicating the first control ports in said second pair of cylinders with the piston chamber in one cylinder of said first pair of cylinders, a fourth pair of control passages communicating the second control passages in the second pair of cylinders with the piston chamber in the other cylinder of said first pair of cylinders, means for supplying fluid under pressure to the main ports in one cylinder of each said first and second pairs of cylinders, and passage means for discharging fluid from the other cylinders of each said first and second pairs of cylinders.

7. The combination of claim 6 wherein said first and second control passages are formed in said casing at one side of the cylinders therein and said third and fourth control passages are formed in said casing at the other side of said cylinders in the casing.

8. The combination of claim 6 including means defining a third and fourth pair of cylinders, piston members in said third and fourth pairs of cylinders defining piston chambers therein and passage means communicating the piston chambers in said first and second pairs of cylinders with respective ones of the piston chambers in said third and fourth pairs of cylinders whereby the fluid control means associated with said first and second pairs of cylinders also controls the fluid flow to the third and fourth pairs of cylinders.

9. A rotary piston type fluid pump or motor comprising a pump casing having a shaft and at least four cylinders extending generally radially from the shaft and angularly spaced apart substantially 90 to provide first pair of cylinders disposed substantially 180 from each other and a second pair of cylinders disposed substantially 180 from each other and substantially 90 from the cylinders of the first pair, a piston member slidably disposed in each cylinder and defining a piston chamber therein, an eccentric cam means on said shaft for controlling cyclic reciprocation of said piston members in successive substantially 90 phase relation to each other, fluid control means individual to the piston members in at least each of said four cylinders, said fluid control means each. including a main port communicating with each cylinder intermediate the ends thereof; a first control port communicating with each cylinder at a point spaced radially inwardly of the respective main port; a second control port communicating with each cylinder at a point spaced radially outwardly of the respective main port; and passage means in each valve member for communicating the main port alternately with said first and second control ports as the piston member reciprocates, a first pair of control passages communicating said first ports in said first pair of cylinders with the piston chamher in one cylinder of said second pair of cylinders, 21 second pair of control passages communicating the second control ports in said first pair of cylinders with the other cylinder of said second pair of cylinders, a third pair of control passages communicating the first control ports in said second pair of cylinders with the piston chamber in one cylinder of said first pair of cylinders, a fourth pair of control passages communicating the second control passages in the second pair of cylinders with the piston chamber in the other cylinder of said first pair of cylinders, a first main passage communicating with the main ports in one cylinder of each said first and second pairs of cylinders, a second main passage communicating with the main ports in the other cylinders of each said first and second pairs of cylinders, means for reversibly supplying fluid pressure to said first and second main passages, said casing having a crankchamber therein communicating with the inner ends of said cylinders, first and second drain passages respectively communicating said crankchamber with said first and second main passages, and a check valve in each drain passage operative to open for flow from the crankchamber and to close to prevent reverse flow to the crankcharnber.

10. A piston type fluid pump or motor comprising, a casing having a plurality of cylinders and a piston member in each cylinder defining a piston chamber at one end of the respective cylinder, a shaft, means on the shaft for controlling reciprocation of the piston members in preselected phase relation to each other as the shaft rotates, means for controlling the supply of fluid pressure to all of said piston chambers comprising a first set of fiuid control means each individual to certain of said piston members, means for controlling exhaust of fluid pressure from all of said cylinders comprising a second set of fluid control means each individual to others of said piston members, each fluid control means of said first and second sets including a main port and first and second control ports and valve means operated by the respective piston member for communicating each main port alternately with the associated first and second control ports, a fluid supply passage communicating with the main ports of the first set of control means and a fluid return passage communicating with the main ports of the second set of control means, and first and second control passages respectively individual to each said first and second control ports, the first and second control passages associated with each piston member being connected to the piston chambers for two different piston members which are reciprocated out of phase with said first mentioned piston member.

11. A piston type fluid pump or motor comprising, a casing having a plurality of pairs of cylinders and a pair of piston members in each pair of cylinders each defining a piston chamber at one end of the respective cylinder, a shaft, means on the shaft for controlling reciprocation of the pistons in preselected phase relation to each other as the shaft rotates, means for controlling the supply of fluid pressure to all of said piston chambers comprising a first set of fluid control means each individual to a first piston of each of at least several of said pairs of pistons, means for controlling exhaust of fluid pressure from all of said cylinders comprising a second set of fluid control means each individual to a second piston of each of said several pairs of pistons, each fluid control means of said first and second sets including a main port and first and second control ports and valve means operated by the respective piston member for communicating each main port alternately with the first and second control ports, a fluid supply passage communicating with the main port of the first set of control means and a fluid return passage communicating with the main ports of the second set of control means, and first and second control passages respectively individual to each said first and second control ports, the first and second control passages associated with each piston member being connected to the two piston chambers for one of said pairs of piston members.

12. The combination of claim 11 wherein the means on the shaft controls reciprocation of the pistons of each pair substantially out of phase with each other.

13. A piston-type fluid pump or motor comprising, a casing having a plurality of pairs of cylinders and a pair of piston members in each pair of cylinders each defining a piston chamber at one end of the respective cylinder, a shaft, means on the shaft for controlling reciprocation of the pistons in preselected phase relation to each other as the shaft rotates, means for controlling the supply of fluid pressure to all of said piston chambers comprising a first set of fluid control means each individual to a first piston of each of at least several of said pairs of pistons, means for controlling exhaust of fluid pressure from all of said cylinders comprising a second set of fluid control means each individual to a second piston of each of said several pairs of pistons, each fluid control means of said first and second sets including a main port and first and second control ports and valve means operated by the respective piston member for communicating each main port alternately with the first and second control ports, a fluid supply passage communicating with the main port of the first set of control means and a fluid return passage communicating with the main ports of the second set of control means, and first and second control passages respectively individual to each said first and second control ports, the first and second control passages associated with said first piston member of each pair of piston members being connected to the two piston chambers for a differentpreselected pair of piston members and the first and second control passages associated with said second piston member of each pair of piston members being connected to the two piston chambers for the same preselected pair of piston members.

14. A piston type fluid pump or motor comprising, a casing having a plurality of cylinders and a piston member in each cylinder defining a piston chamber at one end of the respective cylinder, a shaft, means on the shaft for controlling reciprocation of the piston members in preselected phase relation to each other as the shaft rotates, means for controlling the supply of fluid pressure to all of said piston members comprising a first set of fluid control means each individual to certain of said piston members, means for controlling exhaust from all of said cylinders comprising a second set of fluid control means each individual to others of said piston members, each fluid control means of said first and second sets including a main port and first and second control ports and valve means operated by the respective piston member for communicating each main port alternately with the associated first and second control ports, a firs main fluid supply passage communicating with the main port of said first set of control means and a second main supply passage communicating with the main ports of said second set of control means, means for reversibly supplying fluid under pressure to said first and second main passages, first and second control passages respectively individual to each of said first and second control ports, the first and second control passages associated with each piston member being connected to the piston chambers for two different piston members which are reciprocated out of phase with said first mentioned piston member, said casing having a crank chamber therein communicating with one end of each of the cylinders, first and second drain passages respectively communicating said crank chamber with said first and second main passages, and a check valve in each drain passage operative to open for flow from the crank chamber and to close to prevent reverse flow to the crank chamber.

References Cited in the file of this patent UNITED STATES PATENTS 1,893,825 Ernst Jan. 10, 1933 2,383,060 Hofler Aug. 21, 1945 2,736,267 Mosbacher Feb. 28, 1956 2,931,312 Donner Apr. 5, 1960 3,036,528 Klopp May 29, 1962 FOREIGN PATENTS 464,751 Italy July 21, 1951 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. v3,150,603 September 29 1964 Donald L, Yarger It is hereby certified. that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below Column 6 line 59, strike out "control" second occurrence; llne 60, before 'ports" insert control Signed and sealed this 26th dayof January 1965.,

' (SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. A ROTARY PISTON TYPE FLUID PUMP OR MOTOR COMPRISING A PUMP CASING DEFINING AT LEAST FOUR CYLINDERS, FIRST, SECOND, THIRD AND FOURTH PISTON MEMBERS SLIDABLY DISPOSED IN SAID CYLINDERS AND DEFINING A PISTON CHAMBER AT ONE END OF EACH CYLINDER, FLUID CONTROL MEANS INDIVDUAL TO AT LEAST EACH OF SAID FOUR PISTON MEMBERS, SAID FLUID CONTROL MEANS EACH INCLUDING A MAIN CONTROL PORT AND FIRST AND SECOND PORTS AND VALVE MEANS OPERATED BY THE RESPECTIVE PISTON MEMBER FOR COMMUNICATING EACH MAIN PORT ALTERNATELY WITH THE RESPECTIVE FIRST AND SECOND CONTROL PORTS, A SHAFT, MEANS ON SAID SHAFT CONTROLLING RECIPROCATION OF SAID FIRST, SECOND, THIRD AND FOURTH PISTON MEMBERS IN SUCCESSIVE SUBSTANTIALLY 90* PHASE RELATION, A FIRST MAIN PASSAGE COMMUNICATING WITH THE MAIN PORTS OF THE FLUID CONTROL MEANS ASSOCIATED WITH SAID FIRST AND SECOND PISTON MEMBERS, A SECOND MAIN PASSAGE COM- 